Active grille shutters (AGS) are being incorporated into vehicles in order to help meet stricter fuel economy standards. For example, at higher vehicle speeds, AGS automatically close to block airflow through the engine cooling system to reduce vehicle drag and fuel consumption; when starting a cold engine, AGS remain closed to aid in reaching higher engine temperatures more quickly to reduce vehicle emissions and fuel consumption. AGS may be controlled using feedback AGS position sensors.
A conventional approach for diagnosing an AGS system degradation in a vehicle is shown by Farmer et al. in U.S. Patent Application Publication 2013/0338870 where an AGS diagnostic is performed based on receiving a mechanical fault condition signal and a temperature signal, and an AGS system may be disabled if a mechanical degradation is detected.
The inventors herein have recognized potential issues with such systems. Namely, such systems fail to address AGS operation degradation due to faulty AGS position sensors. Furthermore, when AGS position sensor degradation occurs, disabling the AGS system foregoes any fuel consumption reduction advantages that may be preserved by continuing AGS operation.
One approach that at least partially addresses the above issues includes a method for a vehicle, comprising, during a first condition comprising when an AGS position change over a second interval is less than a threshold position change: stalling an AGS motor for a first interval; calculating a fuel economy change over the first interval; and determining a degradation of an AGS sensor based on the fuel economy change being greater than a threshold fuel economy change over the first interval.
In another example, a vehicle system may comprise: an engine; AGS, including an AGS position sensor and an AGS motor; and a controller, including executable instructions to, in response to an AGS position change being less than a threshold position change during a measurement period, actuate the AGS motor to move the AGS to a more closed position until a stall current is drawn by the AGS motor; calculate a fuel economy increase over a first interval while the stall current is drawn by the AGS motor; and determine a degradation of the AGS position sensor based on the fuel economy change being greater than a threshold fuel economy increase.
In another example, a method for a vehicle, executed by an onboard vehicle controller may comprise: in response to an AGS position change being less than a threshold position change during a measurement period, actuating an AGS motor to move the AGS to the more closed position until a stall current is drawn by the AGS motor; calculating a fuel economy increase over a first interval while the stall current is drawn by the AGS motor; and determining a degradation in an AGS sensor based on the fuel economy increase being greater than a threshold fuel economy increase.
In this way, a technical result may be achieved in that degradation modes of the AGS including faulty AGS position sensors or a mechanical AGS degradation can be distinguished. Furthermore, in the event of an AGS position sensor degradation, the AGS position can be inferred so that operation of the AGS and the fuel consumption reduction advantages conferred therefrom can be preserved. Further still, inferring the AGS position via AGS motor stall current is more reliable over both higher and lower ambient temperatures as compared to inference of AGS position via engine temperature changes. The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.